Human Immunodeficiency Virus, type 1 (HIV) is the etiologic agent associated with acquired immunodeficiency syndrome (AIDS). It is lymphotropic for cells expressing the CD4 molecule.
In vitro infection by HIV can be blocked by serum antibodies obtained from infected individuals (1-3), although a precise relationship between antibody titers and disease course is not presently apparent. Several reports have also demonstrated that HIV-neutralizing antibodies can be developed against various immunogens, including glycoprotein extracts (4), recombinant proteins (5-6), and synthetic peptides (1, 7-8). These antibodies react with HIV env gene products, thus solidifying the role of viral surface glycoproteins and cell receptor interactions. In addition, antibodies to the CD4 molecule are capable of inhibiting viral binding activity, as are antiidiotypic reagents to these antibodies (9).
Although HIV envelope glycoproteins are of strong interest with respect to viral inhibition, recent information indicates that gag-encoded proteins may participate as a target for the neutralizing immune response. Gag encodes for a precursor protein of 55,000 molecular weight (p55) which is further degraded into three small proteins with molecular weights of approximately 17,000, 24,000 and 15,000 (p17, p24 and p15, respectively). These three proteins are termed the viral "core" proteins.
The present invention is related to polypeptides found in the p17 core protein of HIV. As demonstrated previously (17) the p17 core protein is comprised of 132 amino acids (more or less depending upon the strain of HIV examined) (FIG. 5), and residues at the 5' end of the gag gene of HIV and at the amino terminal portion of the p55 precursor protein. Certain regions of the p17 core protein (amino acid residues #88-115; TVAT . . . KKKA), exhibit homology with a peptide hormone produced by the human thymus termed thymosin alpha-1 (28). The same authors showed that antiserum to thymosin alpha-1 can neutralize the replication of HIV in vitro, as accounted for by the partial sequence homology between the hormone and the HIV p17 core protein. Further, heterologous antiserum to a 30-amino acid synthetic peptide analogue reacted with the p17 core protein of HIV in a manner identical to that seen with an HIV p17-specific antibody (12).
Previous work had resulted in the isolation of monoclonal antibodies against the p17 protein and the demonstration that those monoclonal antibodies could neutralize the virus. Nevertheless, the p17 protein is a relatively large entity of approximately 132 amino acids. The current invention reflects the discovery (described below in the Examples section) that certain short polypeptides, approximately 11 amino acids or even less in length, are the only ones that react with some monoclonal antibodies capable of neutralizing the biological activity of the HIV virus. The discovery that such short sequences exist and the identification of their structure allows one to construct proteins made exclusively or predominantly of antibody-reactive sequences and to use them as either diagnostic agents or inducers of anti-HIV antibodies. The resulting anti-HIV antibodies can, in turn be used to induce anti-idiotype antibodies themselves useful as antibody inducers.
The presently described immunoreactive polypeptides correspond to the following amino acids, numbered as to their position in the p17 protein (See FIG. 5 for the p17 sequence):
______________________________________ Amino acid numbers in p17 ______________________________________ Polypeptide #1 12-19 Polypeptide #1a 12-17 Polypeptide #1b 13-18 Polypeptide #1c 14-19 Polypeptide #2 17-22 Polypeptide #3 12-22 Polypeptide #4 100-105 ______________________________________
When administered in the presence of adjuvants and/or carrier proteins, these peptides represent HIV vaccines of use to control or inhibit the spread of HIV contagion. In similar form, these peptides represent valuable immunogens with which to generate antibodies of use as diagnostic reagents. Alternatively, they can be used diagnostically to detect anti-HIV antibodies. Further, anti-HIV peptide antibodies are of use to develop anti-idiotype antibodies which themselves represent HIV vaccines when administered in the presence of appropriate adjuvants and/or carrier proteins.
Peptides #1, 1a, 1b, 1c, 2 and 3 represent sequences from the amino terminal region of the p17 HIV core protein. (i.e. the 5' region of the gag gene of HIV). Peptide #3 represents a combination of peptides #1, 1a, 1b and 2. Peptide #4 represents a region of the p17 core protein which bears some sequence homology to the thymic hormone, Thymosin alpha-1.